WattSatt from Fujikura Rubber is a primary magnesium (Mg)-air battery that generates electricity when salt water is used. The battery WattSatt is specially designed for for emergency use. The battery can be used at hospitals, evacuation sites etc at the time of disaster. The battery WattSatt comes with five USB ports. The main unit of the battery is covered with a plastic cover, which is used as a water container for producing electricity. 2L of water is mixed in the container to make an electrolyte solution.The electrolyte solution is poured into the main unit. Besides tap water even sea water and unclean water can be used. The battery incorporates three cells connected in series and has a capacity of 280Wh. It can fully charge 30 smartphones with a capacity of about 2,000mAh each. Mg-air battery is a kind of metal-air battery that uses Mg for its negative electrode and oxygen in the air as a positive-electrode active material.Battery generates electricity by exploiting the phenomenon that Mg is bonded to hydroxide ions and emits electrons. WattSatt battery measures 210 (W) x 143 (D) x 210mm (H) and weighs 1.9kg (without water). The battery scheduled to be released in Japan this summer for approximately ¥20,000 to 30,000 (approx US$176-265).